U.S. Pat. No. 7,427,872 (Patent Document 1) and U.S. Pat. No. 8,212,587 (Patent Document 2) disclose inventions of transmitters and receivers that are capable of performing signal transmission conforming to the Universal Serial Bus (USB) 3.1 standard. The transmitters described in these documents are devices that transmit differential signals to a receiver via differential signal lines having AC coupling capacitors provided in the middle thereof, and have an RX-Detect function that detects whether the receiver is connected to the differential signal lines in a receivable state.
The present inventors have found that the transmitters described in Patent Documents 1 and 2 may perform erroneous detection upon RX-Detect.
The present disclosure describes a transmitter capable of suppressing erroneous detection upon RX-Detect, and a transmission/reception system including such a transmitter and a receiver.
A transmitter according to one aspect of the present disclosure is a transmitter that transmits differential signals to a receiver via differential signal lines having AC coupling capacitors provided in middle of the differential signal lines, and includes (1) an output driver configured to output the differential signals to the differential signal lines; (2) first termination resistors and a first switch, the first termination resistors and the first switch being provided in series between a first reference voltage input terminal and the differential signal lines, a reference voltage being inputted to the first reference voltage input terminal; (3) a pulse generator configured to output a common-mode pulse to the differential signal lines during a period during which a pulse output instruction signal is at a significant level; and (4) a detector configured to output a detection result signal indicating a magnitude relationship between a voltage level of the common-mode pulse and a threshold, during a period during which the pulse output instruction signal is at a significant level, and output a detection result signal indicating that the voltage level of the common-mode pulse does not exceed the threshold, during a period during which the pulse output instruction signal is at a non-significant level.